Update: stable-channel empty tag list fails with message, not silently

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QKxGW1raAWaqeU8WdHsMsp

bin/omarchy-cn-update

@@ -39,7 +39,7 @@ beta)
   git -C "$src" checkout -q "$tag"
   ;;
 stable)
-  tag=$(git -C "$src" tag -l "*-cn.*" | grep -vE "alpha|beta|rc" | sort -V | tail -1)
+  tag=$(git -C "$src" tag -l "*-cn.*" | grep -vE "alpha|beta|rc" | sort -V | tail -1 || true)
   if [[ -z $tag ]]; then
     echo "当前尚无 stable 发布（omarchycn channel beta 可跟随预发布）" >&2
     exit 1